Why won't rest of the PCI-e slots get detected after installing a graphic card in the x4 slot?

I am setting up a mining rig comprising of 5 graphic cards using this mainboard, Gigabyte P35-DS3P. It has the following number of PCI-e slots, as seen in the Gigabyte link:

1x x16 PCI-e slot

3x x1 PCI-e slots

1x x4 PIC-e slot

I have been able to plug in 4 graphic cards using powered PCI-e risers/extenders, in the following order and they work fine:3x R9 280x cards in each of the x1 slot.1x R9 280x card in the x16 slot using x1 riser cable.

Now when I plug in the 5th card in x4 slot, only 1 card would get detected in Windows's 'device manager' section i.e. the one plugged in the x4 slot. I have tried installing it with and without the risers but same results.

Hi @o0ragman0o, thanks for your reply. Actually, I don't need to hotwire since the x1 slots are already getting detected. I took your advice nonetheless but no success. All x1 slots disappear from the Device Manager once the GPU is installed in the x4 slot, on-board or via riser cables.

Man, the motherboard situation is a disaster. I've been using a particular Gigabyte that worked without issues with 6 GPUs active (I have 3 rigs that use it).

But, they've apparently stopped making it, so I ordered an MSI Intel-based (Z170-A PRO LGA 1151) and it's a disaster.

It has 6 PCIe slots, but with all 6 GPUs plugged in, it only recognizes 5 of them and the onboard NIC doesn't work. WTF?

And there is no option in the bios to disable some of the SATA ports, which are also on the PCIe bus.

So, in order to get the 6th GPU recognized, I had to disable the onboard NIC, but that leaves me without networking, which is obviously required. So, I had to order a USB NIC (since the USB doesn't run through the PCIe bus). Total disaster.

But, they've apparently stopped making it, so I ordered an MSI Intel-based (Z170-A PRO LGA 1151) and it's a disaster.

It has 6 PCIe slots, but with all 6 GPUs plugged in, it only recognizes 5 of them and the onboard NIC doesn't work. WTF?

Were you able to see the 6th card in the 'device manager' or 'lspci' prior to disabling the onboard NIC? Did you also have to use the '6gpu mod' to get it to work and did you eventually got the 6th card working?

It's a rock solid MOBO. Never had to mess with anything in the BIOS. All 6 cards detected on first try, onboard LAN works with the cards present, etc. Even has a power button on the board, which is nice.

But, they've apparently stopped making it, so I ordered an MSI Intel-based (Z170-A PRO LGA 1151) and it's a disaster.

It has 6 PCIe slots, but with all 6 GPUs plugged in, it only recognizes 5 of them and the onboard NIC doesn't work. WTF?

Were you able to see the 6th card in the 'device manager' or 'lspci' prior to disabling the onboard NIC? Did you also have to use the '6gpu mod' to get it to work and did you eventually got the 6th card working?

Prior to disabling the onboard NIC, lspci would only list 5 of the GPUs. After disabling the NIC, the 6th one showed up.

I wasn't able to mine though, because I didn't have a damn network connection at that point.

Have a USB wireless NIC arriving today intended for another rig, but will hijack it until tomorrow when the USB wired NIC shows up. Talk about a 3-ring circus!